In an effort to provide extra nutrition to your garden soil, you could inadvertently be adding harmful chemicals. Use these tips to make smarter fertilizing decisions.

The first garden we put in at our farm was the result of tilling under a lawn that had been heavily fertilized before we moved in. Surprisingly, we had relatively little trouble with grass in the garden and had a very rewarding year. Our garden grew seemingly without much aid from us. The squash plants had elephant-ear sized leaves, the corn grew tall and lush, and we ate all we could, consigning much more to the compost pile.

I laugh at that woman now. The woman who didn’t realize that garden was a cruel trick of chemical-fertilizer residues. That year’s garden was like the sugar rush you see in a child who has just eaten a large cupcake. The next year and the years to follow have been the inevitable sugar crash.

As your soil goes, so goes your health. If your soil is deficient in minerals and you eat the food that grows there, you will also be deficient in those minerals. It’s impossible for plants to make up their bodies with minerals they cannot access. One of the biggest mistakes that we make in gardening is to rely solely on a bag of fertilizer that only tells us the N-P-K ratio. At some point, scientists got together and determined that nitrogen, phosphorus and potassium were the only nutrients the average gardener should feed to their soil. Focusing solely on nitrogen produces lush greenery but overlooks the fact that lush greenery is just window dressing without minerals, such as calcium and magnesium.

So, what kinds of soil additives should we use and which should we avoid? This becomes quite a challenge in today’s polluted world. Here are some problematic soil conditioners that you should understand fully before adding them to your garden.

Nitrogen and Juglone Sawdust is readily available and often mulched around plants for weed repression or added to soil as an amendment. In the right situation, it can be the perfect amendment. If you have soils with high nitrogen content, adding sawdust will leach this nutrient from your soils. However, for most soils, as this mulch pulls down the nitrogen levels, you will begin to see plants fail unless you also apply a high-nitrogen compost. Low nitrogen levels are particularly harmful for leaf crops, such as lettuce or kale.

Also be aware of what type of sawdust you are using. Did the facility mill treated lumber? Is the sawdust a waste product from a furniture industry that has loaded it with toxic polishing treatments? What type of tree is the sawdust made from? Walnut sawdust can inhibit plant growth, especially of those in the rose, nightshade and cabbage families, because of the chemical juglone.

Alternatives: Rake up and use the grass cuttings from your yard. Make your own compost. If you choose sawdust, know your source.

Phosphorus Many high-phosphorus fertilizers are approved for use under organic standards. They’re intended to encourage vigorous root growth and thereby result in abundant plant growth and high yields. Unfortunately, this hasn’t always been the case. In fact, in some instances these additives have been shown to retard plant growth instead.

The real downside to using these imbalanced fertilizers is that the mycorrhizae in the soil work best in an environment that contains low levels of phosphorus. It doesn’t actually kill these extremely important soil workers, but it creates an environment in which they do not germinate or grow.

Alternatives: Use a balanced fertilizer or, better yet, perform a thorough soil test. Once you understand the levels of nutrients in your soil, you can choose which need to be increased or decreased to attain balance.

Persistent Herbicides (Aminopyralid, Clopyralid and Picloram) Many organic gardeners use hay for weed suppression. Unfortunately, over the past several years, we’ve seen an increase in the use of aminopyralid, a persistent herbicide, on hay fields. These non-specific chemicals remain on cut hay and forage, and when added to your garden, they’ll continue to act on “weeds,” such as your tomatoes and peas. Unfortunately, shortly after the issue with hay and forage was discovered, manure also became a problem. This was not only because of the presence of contaminated bedding but also because the herbicides clopyralid and picloram were found in commercial animal feed.

Alternatives: As you weed, lay the wilted leaves and stems down as mulch. Make your own compost to use as mulch and soil additives, as well. Know the source of your manure, if you use it, and ask what they are feeding, where the animals are grazing and what has been sprayed there.

About the Author: Dawn Combs has more than 20 years of ethnobotanical experience, is a certified herbalist, and has a bachelor’s degree in botany and humanities/classics from Ohio Wesleyan University. She is co-owner of Mockingbird Meadows, a medicinal herb and honey farm near Columbus, Ohio, where she consults with women and their partners on issues of hormonal imbalance, oversees the United Plant Savers Botanical Sanctuary and operates the Ohio Eclectic Herbal Institute.

Product Spotlight

Dawn is a wife, mother, farmer, author, ethnobotanist, professional speaker and educator. She has over 20 years of ethnobotanical experience, is a certified herbalist and has a B.A. in Botany and Humanities/Classics. Dawn is co-owner of Mockingbird Meadows, the home farm for her educational web channel Heal Local. She is the author of Conceiving Healthy Babies: An Herbal Guide to Support Preconception, Pregnancy and Lactation (New Society Publishers, 2014) and Heal Local: 20 Essential Herbs for Do-it-Yourself Home Healthcare (New Society Publishers, 2015).FOLLOWMORE ARTICLES